Distribution of alphavbeta3, alphavbeta5 integrins and the integrin associated protein--IAP (CD47) in human glomerular diseases

The alphav integrins present on the membrane of numerous cells, mediate attachment to matrix proteins, cell proliferation, migration and survival. We studied the expression of alphav integrinis and CD47 (a beta3 chain integrin associated protein) in various forms of glomerulonephritis (GN) characterized by mesangial proliferation and/or increased mesangial matrix. In normal glomeruli, epithelial cells expressed alphavbeta3, alphavbeta5 and CD47; endothelial cells expressed alpha5beta1 and CD47; mesangial cells expressed alphavbeta5, CD47, and to a less extent alphavbeta3. In acute post infectious GN (APIGN), membrano-proliferative GN (MPGN) and diabetic nephropathy(DN), we observed that the beta3 chain, normally expressed by mesangial cells, was not detectable in the mesangium while its expression by epithelial cells was not modified. Parallel to the disappearance of alphavbeta3, the CD47 expression was decreased on the mesangial cells in MPGN, APIGN and DN. The expression of alphavbeta5 was clearly increased on podocytes and on proliferating mesangial cells in APIGN. By contrast, the mesangial expression of alphavbeta was normal or decreased in DN. The alpha5 chain of integrin, absent on normal mesangial cell, was expressed on proliferating mesangial cells in MPGN and APIGN. Thus, we observed modifications of alphavbeta3 and alphavbeta5 expression during human GN. The modulations of alphavbeta3 and alphavbeta5 expression differed according to the different glomerular cell types and were not parallel in glomerular cells: alphavbeta3 was decreased (and alphavbeta5 unchanged) on proliferating mesangial cells and alphavbeta5 was increased (and alphavbeta3 unchanged) in podocytes. This may reflect the existence of two distinct regulatory pathways.